For many years efforts have been made to remove a variety of substances from various surfaces such as rust from metal and various contaminants from concrete and the like. Using high pressure water blasters with or without abrasive particles and high pressure air with sand or other particles to clean surfaces of rust and the like have long been known. These methods have been generally effective but in certain instances have been less than satisfactory. Sand blasting with air has been particularly difficult because of injury from inhaling the silicone particles and with high pressure air or high pressure water because of the need to recover and dispose of the sand which becomes contaminated with the material removed. Sodium chloride or common table salt has been found to be an effective abrasive when used with high pressure water, particularly because of its solubility in water. However, because of its hydroscopic nature, salt has a tendency to gain moisture and become clogged in the supply lines and/or the nozzle and not provide the steady stream desired for blast cleaning.
The present invention provides a method and apparatus for continuously accelerating the salt particles from the supply source to the high pressure nozzle and thus not becoming aglomerated into slugs which interrupt the blast cleaning operation. The nozzle of the present invention creates a vacuum effect in the supply line for drawing the salt particles from the supply and, by means of a flow regulator, the flow of particles is regulated so as to be accelerated from the supply source all the way to the nozzle chamber wherein the particles are mixed with the high pressure liquid. The flow regulator includes variable flow means to modulate the vacuum effect in the flow lines by aspirating air so as to provide a steady flow of accelerated particles through the supply line and with this variable control, it has been found that this desirable effect can be accomplished with flow lines of various lengths.